1. Field of the Invention
The present invention relates to a color filter suitable for a color liquid crystal display used in color televisions, personal computers, etc., and a method of manufacturing the color filter. The present invention also relates to a liquid crystal device employing the color filter.
2. Description of the Related Art
Recently, needs for liquid crystal displays, in particular, color liquid crystal displays, have shown a strong tendency to increase more and more with development of personal computers, in particular, portable personal computers. However, a cost-cutting is required to achieve more widespread use of those personal computers, and a demand for cutting down the cost of, especially, a color filter, which has a relatively great proportion in total cost, has increased.
Various methods have been hitherto tried to meet such a demand while ensuring requisite characteristics of a color filter, but a method capable of satisfying all of the requisite characteristics has not yet been established. Those conventional methods will be described below.
The first one of widely employed methods is a dyeing method. According to the dyeing method, a water-soluble polymeric material is first applied as a dyeing material to the surface of a glass substrate. The applied polymeric material is patterned into the desired form by photolithography. The resulting pattern is immersed in a dyeing bath to obtain a colored pattern. By repeating the above process three times, color filter layers of R (red), G (green) and B (blue) are formed.
Japanese Patent Laid-Open No. 5-288913 discloses another example of the dyeing method. According to the disclosed method, a photosensitive layer is formed on a substrate and exposed to light for patterning. An unexposed portion of the photosensitive layer is then dyed. By repeating the above process three times, a color filter having a three-layered structure of three colors, i.e., R, G and B, is manufactured.
Further, Japanese Patent Laid-Open No. 5-188215 and No. 5-273410 disclose a method of fabricating a color filter of R, G and B by using a polysilane layer as a color filter forming layer and repeating exposure for patterning three times.
The second one is a pigment dispersion method that has been more commonly used instead of the dyeing method in recent years. According to the pigment dispersion method, a photosensitive resin layer containing a pigment dispersed therein is first formed on a substrate, and a pattern of a single color is then obtained by patterning the photosensitive resin layer. By repeating the above process three times, color filter layers of R, G and B are formed.
The third one is an electrodeposition method. According to the electrodeposition method, a transparent electrode is first formed on a substrate by patterning, and the substrate is immersed in an electrodeposition coating solution including a pigment, a resin, an electrolyte, etc., thereby electrodepositing a first color layer. Color filter layers of R, G and B are formed by repeating the above process three times, and are finally fired.
According to the fourth method, a pigment is dispersed in a thermosetting resin, and printing is repeated three times using the resulting resin to separately coat resin layers of R, G and B. The resin is then thermally set to form colored layers. Additionally, in any case employing the above-described methods, it is usual to form a protective layer on the colored layers.
A point common to the above conventional methods is that the same process must be repeated three times to form three colored layers of R, G and B, and a production cost is increased correspondingly. This raises such a common problem that yield is reduced due to an increased number of steps. Further, the electrodeposition method is not suitable for manufacture of TFT displays because pattern shapes capable of being formed by the electrodeposition method are limited in the current state of art. In addition, the printing method is difficult to form a fine pitch pattern because of poor resolution.
To compensate for the above-described drawbacks of the conventional methods, Japanese Patent Laid-Open No. 59-75205, No. 63-235901 and No. 1-217302 disclose methods of manufacturing color filters using the ink jet technique, but a satisfactorily feasible method has not yet been realized.
An object of the present invention is to provide a color filter manufacturing method which can manufacture a color filter inexpensively with the reduced number of steps while satisfying requisite characteristics of the color filter, e.g., heat resistance, resistance to solvent and resolution, as with conventional methods. Another object of the present invention is to provide a highly reliable color filter manufactured by the above method, and a liquid crystal device constructed by using the color filter.
More specifically, the present invention is intended to prevent color mixing, color unevenness and uncolored dots which may occur in forming colored portions using the ink jet technique, and to provide a color filter with high reliability.
The above objects of the present invention are achieved with features as follows.
A color filter manufacturing method according to the present invention comprises the steps of forming, on a substrate, a photosensitive layer that increases or develops hydrophilic property upon irradiation of light; exposing the photosensitive layer to light for patterning to form hydrophilic areas in which hydrophilic property is relatively high and non-hydrophilic areas in which hydrophilic property is lower than the hydrophilic areas; and applying a setting ink to the hydrophilic areas with an ink jet technique, thereby forming colored portions.
A color filter according to the present invention includes at least a photosensitive layer formed on a substrate and having hydrophilic areas in which hydrophilic property is increased or developed upon irradiation of light, and colored portions formed on the hydrophilic areas of the photosensitive layer.
A liquid crystal device according to the present invention comprises a liquid crystal held between a pair of substrates, one of the substrates being constituted by using the color filter of the present invention.